The present invention relates generally to filter media construction, particularly construction wherein the filter media has a generally flat configuration for use in panel filters or any similar application where flat filter surfaces are required.
In a typical conventional flat filter media construction, a series of pairs of generally flat sheets of a suitable filtering material (e.g. paper) are mounted in spaced, parallel relation to one another to leave a spacing between the facing surfaces of each such pair of sheets, and the two sheets in each such pair are also spaced from one another to provide an interior spacing therebetween. An air stream having foreign matter entrained therein is caused to flow into the spacings between adjacent pairs of filter sheets, then inwardly through the facing surfaces of each adjacent pair of filter sheets to the interior spacing thereof, whereby the foreign matter is deposited on such facing surfaces, and the cleaned air is caused to flow away from the interior spacing of each pair of sheets.
Because the sheets of filter media are generally made of a flexible material such as paper, and because the aforesaid air flow through the filter media creates a pressure drop across the sheets, the two sheets in each pair of sheets tend to collapse toward one another, which can reduce or even eliminate the required spacing therebetween that forms the aforesaid clean air interior area between the sheets. Similarly, since each pair of sheets is located in close proximity to the adjacent pairs, the flexing movement of the filter media can also result in a significant reduction in the aforesaid spacing between the facing surfaces of adjacent pairs of filter sheets thereby reducing the size of the area between the pairs of filter sheets that is necessary for receiving the dirty air with entrained foreign matter.
To avoid these problems, conventional filter media constructions incorporate in each of the filter media sheets a plurality of dimples or indentations that are arranged in a predetermined pattern to maintain the desired spacing not only between the two sheets in each pair, but also the facing sheets of adjacent pairs. More specifically, the two sheets in each pair both include inwardly directed dimples, and the dimples in both sheets are located directly opposite one another so that if the two sheets tend to collapse toward one another, the opposed dimples can abut one another and maintain the desired spacing between the sheets. Similarly, the outwardly facing surfaces of each pair are formed with outwardly directed dimples, and such dimples in one pair are located directly opposite the corresponding outwardly projecting dimples in the facing surfaces of an adjacent pair to maintain, in a similar manner, the dirty air spacing between adjacent pairs of filter media sheets.
In typical known filter media constructions, the inwardly directed dimples in each sheet alternate with the outwardly directed dimples so that the inwardly directed dimples in the facing surfaces of adjacent pairs are opposite one another, as are the outwardly directed dimples. While this media construction effectively solves the problem of maintaining the desired spacings as described above, it also results in significant drawbacks in some filtering applications of the filter media.
For example, where the foreign matter to be filtered is somewhat large in particulate size, such as the textile waste material that becomes entrained in the ambient air in textile mills and the like, the opposed inwardly facing dimples in the facing surfaces of adjacent pairs form opposed crevices that tend to collect clumps of foreign matter therebetween, and the opposed crevices at each end of the clump tend to anchor the clump in place so as to make it very difficult to remove the clump using traditional filter cleaning systems (e.g. pressurized air directed against the filter surfaces to be cleaned). Additionally, the opposed inwardly directed dimples in each pair of filter media sheets can, in some filtering applications, result in a larger interior spacing between the sheets than is required, which will result in an unnecessary increase in the size and expense of the overall filtering apparatus which normally consist of a substantial number of adjacent pairs of filter media sheets.
The present invention provides a filter media construction that avoids the aforesaid drawbacks of conventional filter media constructions.